1. Field of the Invention
The present invention relates to a recording disc, and, more particularly, to a method for seeking a target position on a multi-layer disc.
2. Background of the Related Art
Optical discs such as digital versatile discs (DVDs) have become commonly used. Such discs are capable of recording and reproducing high duration, high quality video data and audio data. These optical discs can be a reproduction-dedicated DVD-ROM, once recordable DVD-R and DVD+R, and recordable DVD-RW, DVD+RW, DVD-RAM, or the equivalent. Blue-ray discs have a relatively higher recording density than the optical discs. An optical disc or a blue-ray disc may be multi-layer discs having a first recording layer, Layer 0, a second recording layer, Layer 1, and are often used to increase the amount of recordable data that may be recorded on an optical disc.
A disc device, such as, for example, a DVD-Recorder, is capable of recording or reproducing data on the optical disc or blue-ray disc. As shown in FIG. 1, the DVD-recorder includes an optical disc 10, an optical pick-up 11, a spindle motor 12, a sled motor 13, a motor driving unit 14, a servo controller 15, a micro-computer 16, a memory 17 and a video disc record (VDR) system 18. The microcomputer 16 controls operations of the VDR system 18 such that data recorded on the optical disc 10 can be reproduced from the optical disc 10 or data from the outside can be recorded on the optical disc 10.
As shown in Fig. 2 when a multi-layer disc 10, such as a DVD+R dual layer, is inserted in the optical disc device and a data recording operation is performed, the VDR system 18 operates such that data is recorded on a first recording layer, Layer 0 of the multi-layer disc 10 from an inner circumference to an outer circumference of the disc 10.
When all of the data area allocated in the first recording layer, Layer 0, which is between the inner circumference of the disc 10 and a middle area formed between layers proximate the outer circumference of the disc 10, is filled, the micro-computer 16 controls operations of the servo controller 15 such that the optical pick-up 11 can perform a layer jump to access the second recording layer, Layer 1. After that, the VDR system 18 operates such that data can be recorded in the second recording layer, Layer 1 of the disc 10 from the outer circumference to the inner circumference of the disc 10.
When the micro-computer 16 performs a seek operation to move the optical pick-up 11 from a current position of the first recording layer, Layer 0, to a target position of the second recording layer, Layer 1, it controls operations of the servo controller 15 such that the optical pick-up 11 performs a layer jump operation to access the second layer, Layer 1, and then horizontally moves to the target position. Similarly, as shown in FIG. 4, when the micro-computer 16 performs a seek operation to move the optical pick-up 11 from a current position of the second recording layer, Layer 1, which is close to the middle area, to a target position of the first recording layer, Layer 0, it controls operations of the servo controller 15 such that the optical pick-up 11 performs a layer jump operation to access the first layer, Layer 1, and then horizontally moves to the target position.
The middle areas, which are allocated to the first and second recording layers, Layers 0 and 1, respectively, are protection areas such that data is preferably not recorded in the outermost circumferential region of the disc 10. The middle areas preferably prevent the optical pick-up 11 from escaping the boundaries of the recording area while data are recorded in the first recording layer. The size and position of the middle area is predetermined in a multi-layered disc.
The disc may be finalized based on a single recording operation. However, if the disc is not finalized, a plurality of recording operations may be separately performed on the same disc. In this case, the recording area generated by each recording operation is referred to as a session. Therefore, in the former case, the disc has only one session, whereas in the latter case, the disc has multiple sessions.
As shown in FIG. 5, when data are recorded on a multi-layered disc with multi-sessions, the sessions are separated via an intro area allocated at the beginning of the session and a closure area allocated at the end of the session. An intro area is not allocated to the first session and a closure area is not allocated to the last session. The intro area and the closure area function to separate adjacent sessions, and no data is recorded therein. Therefore, when a desired session is accessed by a seek operation, a data area following an intro area of a corresponding session is directly accessed such that the data therein can be reproduced.
As shown in FIG. 6(a) and FIG. 6(b), when data are recorded on an optical recording disc with multi-sessions, two adjacent sessions may be recorded around the middle area such that portions of the closure area of the former session or the intro area of the latter session may be recorded in both the first recording layer and the second recording layer. An example of a layer jump operation under these circumstances is shown in FIG. 6(a) in which the optical pick-up 11 moves from a first, current position in the first layer to a second, target position in the second layer. In this example, the current position is located proximate a closure area of the i-th session, the i-th session being the last session of the first recording layer, and the closure area is recorded in both the first and second recording layers. The target position is located in the second recording layer and at a horizontal position which is inward relative to the current position. In this situation, upon performing the layer jump operation, the optical pick-up 11 accesses the closure area of the i-th session, which is adjacent to the middle area of the second recording layer 1, or the intro area of the (i+1)-th session, and the layer jump operation generally fails because the optical pick-up 11 encounters a non-data area upon completing the layer jump. Thus, due to the lack of location data in these non-data areas, the optical pick-up 11 cannot detect a corresponding recording position. Therefore, the target position cannot be reached, or seeking the target position is time consuming.
A similar situation is shown in FIG. 6(b). In this example, the current position is located proximate an intro area of the j-th session of the second recording layer with an intro area recorded in both the first and second recording layers, and the target position is located at the first recording layer, at a position which is horizontally inward from the current position. Upon performing the layer jump operation, the optical pick-up 11 accesses the closure area of the (j−1)-th session, which is adjacent to the middle area of the first recording layer, or the intro area of the j-th session, and again encounters a non-data area upon completion of the layer jump, and cannot access the target position.
Additionally, a typical optical recording disc has relatively low recording and reproducing qualities at its outer circumference due to eccentricity and surface vibration, which are greater at the outer circumference than at the inner circumference, and to non-uniform distribution of recording material at the outer circumference. Moreover, the optical recording disc has disadvantages in that servo operations, such as focusing, tracking, layer jumping, and the like cannot be accurately performed.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.